This invention relates to methods and arrangements for emergency braking of a vehicle utilizing an obstacle detection system and an evaluation unit.
To enhance the safety of a car and passengers in present-day road traffic, in addition to providing extravehicular traffic guidance systems, efforts are being made to support the operator in routine driving operations as well as in extraordinary situations using systems that intervene automatically in the control of the vehicle or of particular vehicle components.
A first step in this direction was the adoption of antilock braking systems (ABS) and antislip regulation (ASR) to enhance longitudinal vehicle stability in dynamically critical situations, i.e. in braking and accelerating processes.
In addition, use is made of so-called dynamic regulation (DR) and/or stability regulation (SR) to enhance transverse stability in dynamically critical situations, particularly, that is, in situations brought about and influenced by steering-wheel action taken by the operator. DR evaluates sensor data provided by suitable sensors from particular vehicle components or from the vehicle as a whole and correlates the data using special algorithms. In this way it is possible to recognize transverse dynamically critical situations and, by taking positive action with respect to individual parameters of vehicle dynamics, for example steering-wheel angle, speed and acceleration, to influence the vehicle positively with reference to the transverse dynamically critically situation. Here especially the traction between the tires and the roadway also plays an important part, since the transmission of force between the vehicle and the roadway during vehicle control actions depends directly upon the traction. However, DR acts blindly, so to speak, with reference to the environment of the vehicle, comprising, for example, the road condition and other moving vehicles in the vicinity. Thus DR alone cannot be employed to examine physically meaningful control actions affecting the motion of the vehicle to determine whether the control actions taken will result in meaningful maneuvers with respect to moving vehicles located in the vicinity or to the roadway conditions.
Other systems have been proposed that are intended to avoid collision of a vehicle with an obstacle by controlling acceleration or deceleration and/or by evasive maneuvers. Such systems, termed "collision avoidance systems" (CAS), are intended to guide the vehicle out of collision situations which are detected by sensors, a collision being prevented by a steering action which is not under the control of operator and consequently by steering maneuvers as well as accelerations and/or decelerations of the vehicle which are likewise executed and controlled independently of the operator. U.S. Pat. No. 5,541,590 discloses a neural network that, by evaluating environmental images detected by a CCD camera, continuously scans the surroundings for possible collisions and controls the vehicle speed and steering in response to additional signals representing the state of motion of the vehicle. Another arrangement is disclosed in U.S. Pat. No. 5,461,357 in which, by segmenting the road area to be monitored and incorporating information about the state of motion of the vehicle, rules are derived for avoiding a recognized obstacle by braking and steering operations. The main problem of these proposed systems is the complexity of CAS, which can function dependably only by using a highly developed sensory system in the vehicle and control strategies that also require knowledge, for example, of open escape routes in a given situation. Since evasion and acceleration strategies to be generated can be executed only when there is a maximum of plausible assurance that the reaction can take place without any additional safety risk to the operator and the vehicle, the complexity of design effort and reliability exceeds the limits of what can be accomplished by automotive technology at the present time.
In view of the complexity of CAS and the difficulties in its realization, a number of unitary systems have been proposed whereby individual CAS functions can be accomplished. A number of publications, for example, U.S. Pat. Nos. 5,410,784 and 5,447,363, disclose "automatic distance regulation" (ADR) systems whereby the spacing of a vehicle from other vehicles and/or stationary objects in the direction of vehicle motion can be detected and can be controlled by a controlled braking action. European Patent No. 0 545 437 discloses a method for avoiding collisions between motor vehicles whereby other vehicles located ahead of a vehicle can be detected and the driver can be warned by alarms against an unsafe approach. Since the vehicle having such a detection system is not yet at the minimum safe distance from a vehicle in front when the driver is warned, the driver can himself initiate appropriate braking action. When the distance is less than a minimum allowable distance, the vehicle will then brake automatically so as to maintain the required distance. U.S. Pat. No. 5,473,538 discloses an arrangement in which the behavior of the vehicle being controlled is included in the deceleration strategy so as to prevent unnecessary or even hazardous braking operations. A disadvantage of such systems is that the warning of a collision, or the correction of the motion of a vehicle, takes place consistently and, to a large extent, with no opportunity for the operator to exercise control. Because of the requirements of the regulating algorithm, a controlling action by such systems will take place quite early so that the action, for example braking of the vehicle, need not be executed too abruptly. Hence the system will respond even in situations that a more or less practiced operator would have negotiated himself with no problems. As a result, the operator will experience a repeated automatic intervention in the control of the vehicle, which is actually necessary in only a few cases from his point of view, and will consider such intervention as unwarranted interference so that such systems are unlikely to meet with much acceptance.